Biological variation of ischaemia-modified albumin in healthy subjects

Ischaemia-modified albumin (IMA), as measured by the albumin-cobalt binding (ACB) test, has been cleared by the US Food and Drug administration as a biomarker to exclude the presence of myocardial ischaemia in patients. Although there are a number of published studies detailing the clinical utility of IMA, data on the biological variation of IMA are still lacking. In this study we determined the analytical and biological variance components of ischaemia modified albumin, and compared the distribution of IMA values in our patient population to those provided by the kit manufacturer.

IMA was determined once a week for five consecutive weeks on a cohort of healthy subjects using a colorimetric method, the A CB test on a Roche modular analyser.

The analytical coefficient of variation (CV(A)) was 5%, and the within-subject (CV(I)) and between-subject (CV(G)) biological variations were 3 and 7%, respectively. Analysis of the repeated measures with gender and race (black and Caucasian) as between-subject factors, and weeks (1-5) as the within-subject factor showed that gender had no significant effect on circulating IMA concentrations (p = 0.3146), whereas race did have a significant effect (p = 0.0062). A significant (p = 0.0185) interaction was observed between gender and race.

The ACB test could bring a new dimension to the care and management of patients with acute coronary syndrome. Further studies for normal population distributions by gender and ethnicity, and an optimum cut-off value appear to be required.